This invention relates to an electromechanical system for the treatment of living tissues and/or cells by altering their interaction with their electro-dynamic and electrostatic environments. The invention also relates to a system for the modification of cellular and tissue growth, repair, maintenance, and general behavior by the application of encoded electrical information. More particularly, this invention provides for the application, by surgically non-invasive direct reactive coupling, of one or more electrical voltage and corresponding current signals conforming to highly specific electromagnetic signal patterns. The instant invention, accordingly, relates to the generalized area now known as electromagnetic medicine. That is, the use of electrical signals to modulate rates of in vivo biological growth and of repair processes.
This technology experience a relatively slow growth during the initial phase of its development which, generally, corresponded to the period of 1930 through 1975. The prior art reflective of work in this period is typified by French Patent No. 748,828 (1933) to Siemens which shows the use of a variable-width plate capacitor in an applicator head for use in electromagnetic therapy; and U.S. Pat. No. 2,130,758 (1938) to Rose which teaches the design of electrodes for use in a diathermy machine. Accordingly, diathermy, with its attendant property of penetrating thermal values to human tissue, represents the precursor of present day electromagnetic medicine.
Over time and, particularly, by about 1962, it was established that the effects of diathermy could be achieved by athermapeutic means, that is, means which, to the touch of a patient, did not appear to be transmitting heat or thermal values. Such patents are reflected in U.S. Pat. Nos. 3,043,310 (1964) and 3,181,535 (1965) both to Milinowski, directed to such athermapeutic treatment means. Accordingly, the extension of diathermy, into treatment means in which heating of the skin of the patient was no longer a limitation, enabled a much broader range of electromagnetic signal patterns to become potentially usable, at least experimentally, in the instant area. Use of an athermapeutic apparatus utilizing pulsed high frequency radiation in the range of 27 megacycles, and utilizing oscillations thereof of a sine waveform, is taught in said second Milinowski patent. Therein, Milinowski states that such an athermapeutic apparatus utilizing such pulsed high frequency radiation will produce greater beneficial results than EMF that can be applied without such pulsing of the waveform, particularly, in that heat tolerance is no longer a factor.
The technology of the use of pulsed electromagnetic fields (PRF) in the megahertz range within clinically usable apparatus first appeared in U.S. Pat. Nos. 3,270,746 (1966) and 3,329,149 (1967) both to Kendall, and further in U.S. Pat. No. 3,952,751 (1976) to Yarger, entitled High Performance Electrotherapeutic Apparatus. It is to be understood that the above is reflective of efforts in the prior art to employ bursts of EMF pulses in the megahertz range, this as opposed to other efforts in the prior art to employ bursts of pulses of electromagnetic waves which are in the kilohertz range or lower. It is, accordingly, to be understood that the instant invention does not relate to the area of low RF frequency electromagnetic therapy but, rather, is limited to the use of higher frequency waveforms and, more particularly, waveforms having frequencies in excess of one megahertz.
The use of most so-called low frequency EMF has been with relationship to applications of repair or healing of bone. As such, the EMF waveform and current orthopedic clinical use thereof involve relatively low frequency components and is of a very low power, inducing maximum electrical fields in the millivolts per centimeter (mV/cm) range at frequencies under five kilohertz. The origins of such a bone repair signal began with the early work of Becker, Yasuda, Brighton and Bassett; their work considered that an electrical pathway may constitute a means through which bone can adaptively respond to such an EMF input. This work was followed by a linear physicochemical approach taken by Pilla (one of the within inventors) who employed an electrochemical model of the cell membrane to predict a range of EMF waveform patterns for which bioeffects might be expected. This approach was based upon an assumption that the cell membrane was the most likely EMF target. This effort became one of finding the range of waveform parameters for which an induced electric field could couple to electrochemical, i.e., voltage-dependent kinetics, at the cellular surface. Extension of this linear model involved Lorentz force considerations which eventually led to the suggestion that the magnetic field along could be considered the dominant stimulus in EMF/PRF electrotherapy. These thoughts results in ion resonance and quantum theories that predicted benefits from combined AC and DC magnetic field effects at very low frequency ranges. This area of research is reflected in U.S. Pat. Nos. 4,105,017, 4,266,532 and 4,266,533, all to Ryaby, et al.
A second therapeutic EMF method to which the instant invention is more directly concerned, involves the use of a shortwave pulsed radio frequency (PRF) signals having a microsecond burst of megahertz sinusoidal waves with such bursts repeating between 0.01 and 1000 Hertz, and inducing a maximum electrical field in the volts-per-centimeter range at tissue level.
As above noted, a PRF signal derived from a 27 MHz continuous sine wave used for deep tissue healing is known in the prior art of diathermy and its above reference non-thermal successors thereto. A pulsed successor of the diathermy signal was originally reported by Giazberg as an electromagnetic field capable of eliciting a non-thermal biological effect in the treatment of infections. Since that original work, PRF therapeutic applications have been reported for the reduction of post-traumatic and post-operative pain and edema in soft tissues, wound healing, burn treatment, and nerve regeneration. The application of EMF for the resolution of traumatic edema has become increasingly used in recent years. Results to date using PRF in animal and clinical studies suggest that edema may be measurably reduced form such electro-physical stimulus.
Two general mechanisms have been proposed for the effect of PRF on edema. The first suggest that EMF affects sympathetic outflow, including vasoconstriction, which restricts movement of blood constituents from vascular to extravascular compartments at the injury site. The second proposes that the passage of electrical current through the tissue displaces the negatively charged plasma proteins found in the interstitium of traumatized tissue. This increase mobility, it is suggested, operates to accelerate protein uptake by the lymphatic capillaries, thereby increasing lymphatic flow which is an established mechanism for extracellular fluid uptake resultant from traumatic edema.
The within invention is based upon biophysical and animal studies which attribute the effect of cell-to-cell communication on the sensitivity of tissue structures to induced voltages and associated currents. These studies have established that prior art considerations of EMF dosimetry have not taken into account the dielectric properties of tissue structure (as opposed to the properties of isolated cells). The implications thereof are that a proper, i.e., an efficient reactive coupling of a PRF signal to tissue has not heretofore been effected in the art of record. This art, as is typified in the efforts of the last ten years relative to high frequency PRF, is reflected in U.S. Pat. Nos. 4,454,882 (1984) to Fellus, entitled Electrotherapeutic Apparatus; 4,674,482 (1987) to Waltonen, entitled Pulsed Electromagnetic Field Therapy Device; 4,998,532 (1990) to Griffith entitled Portable Electro-Therapy System; and 5,014,699 (1991) to Pollack et al, entitled Electromagnetic Method and Apparatus for Healing Living Tissue.
In recent years the clinical use of non-invasive PRF at radio frequencies has consisted of the use of pulse bursts, such pulses having a sinusoidal or other form, and at a frequency of 27.12 MHz, each such pulse burst typically exhibiting a width of sixty-five microseconds and containing a range of 1,100 to 10,000 pulses per burst, and with a pulse burst repetition rate in the range of 0.01 to 1,000 Hertz. At this high frequency, the burst duty cycle within the respective burst, in existing clinical equipment, has been in the range of one-half to four percent. A defining characteristic burst formed of such megahertz frequency pulses has been that of the configuration of the bi-polar amplitude envelope of the voltage of each pulse burst. This art is reflected in such clinical therapeutic devices as the SofPulse of Magnetic Resonance Therapeutics, Inc., Pompano Beach, Fla.
As noted above, a limitation in the art of record has been that efficient reactive coupling of the PRF signal to the tissue of interest has been difficult to accomplish. The instant invention addresses this problem by means of a system in which the impedance of the applicator head of the PRF apparatus is pre-set to an appropriate range of physiologic impedance and in which the power level of the PRF output of the pulse generating apparatus is continually monitored to thereby assure a closely regulated PRF signal input to the applicator head. This, in combination with tunable reactive means in the applicator head, enables delivery of PRF signal within the appropriate range of physiologic impedance. With such efficient reactive coupling to the tissue to be treated, various advantages of system efficiency and effectiveness of delivered PRF signals are accomplished.